Owing to the actual function of these appliances, which is to position the support for the roof of a mine level, the latter operate in a dangerous area and consequently attempts have been made to keep the operator at a distance from the dangerous area, by automation of the bolting operations. However one condition to be fulfilled is that the operator, kept at a distance in this way, maintains good visibility in the direction of the drilling and/or bolting device.
Bolting appliances are known having a single central driving station, used both for controlling the movement of the appliance on the ground and for controlling the drilling and/or bolting device. A roof for protecting the operator is sometimes provided on these appliances, which roof is stationary and located above the driving station. However, in view of the above mentioned requirements as regards visibility, this design cannot be used universally:
On one hand, the roof must be sufficiently high in order that the operator is able to work in an upright position, so that the arrangement of the appliance in question is suitable solely for working in mine levels of sufficient height. PA1 On the other hand, the solution of the central driving station is in practice reserved for appliances provided with two symmetrical lateral arms supporting the drilling and/or bolting devices.
In other cases, i.e. for mine levels of limited height and where the appliances are provided with a single central arm, another design is preferred, with a driving station directed towards the front for controlling the movement of the appliance on the ground and an operating station on the side, for controlling the drilling and/or bolting device. The driving station, located between the front and rear wheels of the appliance, comprises the steering wheel and the other controls necessary for the movement of the appliance on the ground. The operating station, located on the side of the appliance in front of the driving station, enables the operator to control the drilling and/or bolting device while standing on the ground beside the appliance, which gives him good visibility for controlling the operations.
Mining appliances with a double station, the arrangement of which has just been discussed, in certain cases have a protective roof solely over the driving station. The operating station is not protected and it will be understood that it cannot be protected by means of a stationary device, since this device would project over the side of the appliance and would increase the width of the latter thus impeding its movement on the ground. Thus, the operator is not protected against falling pieces of rock when he is stood at the side of the appliance for controlling drilling and/or bolting and this constitutes a serious omission in the safety precautions.